Such transducers, which are called Planar Loudspeakers or some times Ribbon Loudspeakers, in the past years have not enjoyed the same popularity as the cone-type speakers—in spite of the superior performance of the diaphragmatic types—due primarily their high cost, and the different performance characteristics.
The conventional, cone or dome Loudspeakers are known as electromagnetic motor actuated point sound source emitting devices.
As is known to those skilled in the art of sound reproduction, the “pistonic” operation of cones or domes is not at all secured throughout their operating range, and as a result there may not be a uniform sound emitting activity from the surface of the cone or dome. Sound waves emitted from the peripheral portion of the cone or dome may be out of phase to the emitted sound, from their central part areas, at any given instant. This is an inherent distorting characteristic of cone-dome Loudspeakers, created by the mode of activation and the shape of the activated sound emitting surfaces. An additional distortion producing factor is the moving mass of cone or dome which has to be moved in accordance with the waveform of the audio current.
The demands of the audio signal can be so great in terms of moving speed and acceleration that the inertial masses or weights of the vibrating parts is a significantly limiting factor. As a result the reproduced waveform is greatly affected especially in high frequencies where the relative inertias cannot be met by the electromagnetic motor moving the heavy cones or domes.
The above severe limitations of the motor actuated Loudspeakers, such as kinetic sluggishness, shape and mass, are certainly overcome by the thin diaphragm type of loudspeaker, which employs as its sound emitting surface a diaphragm of greatly reduced mass and the moving force is applied on almost all the area of the vibrating diaphragm, thus realizing a true pistonic vibration action. The low mass of the diaphragm obeys the commands of the audio waveform with exceptional ease and the acoustic results are extreme fidelity and transparency.
Numerous types of such planar speakers can be found in use in Hi Fi systems giving very satisfactory acoustic results. Most of the planar transducers existing in commercial production today make use of a Polyester or Polyimid diaphragm which has on its surface laminated a very thin layer of parallel aluminum current carrying conductors. The diaphragm is evenly stretched over rows of magnets, the magnetic lines of which intersect the diaphragm with current currying conductors at 90°. The interaction of the magnetic lines and the magnetic field created by the current flowing through the conductors results in a force, moving the diaphragm either forward or backward in accordance with the direction—at any instant—of the flowing audio current.
Such planar loudspeakers are characterized by distinct advantages in performance over the cone-dome loudspeakers. Planar loudspeakers exhibit wider bandwidth, Linear phase response, constant impedance, greatly improved transient response and lower distortion.
All those operating advantages are the reasons of the acoustic superiority of planar loudspeakers. Because of today's digital sources of audio reproduction such as CD, DVD-Audio, SACD (Super Audio CD), DAT etc. which place higher demands on the contemporary loudspeaker systems, the above described advantages are invaluable. However all those acoustic benefits offered by planar magnetics are enjoyed by audiophiles, after paying the high cost, for the loudspeakers.
The high cost of the planar loudspeakers is acceptable to audiophiles after considering their distinct acoustic merits. The disappointment of the user may arise, however, if the delicate vibrating diaphragm happens to fail, either by mechanical failure or by thermal failure of the coil. In such situation, the remainder of the expensive structure of the planar loudspeaker is wasted as it is essentially rendered inoperative.
Invariably such planar Loudspeaker failures are not remediable by the user. Under those circumstances the magnetic structure and in fact the entire loudspeaker, for which the audiophile has paid dearly, becomes a total loss or waste. Even in the rare case of loudspeaker makers allowing return to the factory for repair, the user must again pay dearly for material, labor and transportation.